Tube having target with store and/or non-store sections



Oct. 26, 1965 R. H. ANDERSON TUBE HAVING TARGET WITH STORE AND/ORNON-STORE SECTIONS 2 Sheets-Sheet 1 Filed Aug. 6, 1962 Fig. I

Fig. 5 52 IN VE N 70R.

ROBERT H. ANDERSON BUCKHORN, CHEATHAM a BLORE ATTORNEYS R. H. ANDERSONTUBE HAVING TARGET WITH STORE AND/0R NON-STORE SECTIONS 2 Sheets-Sheet 2&

//V VE N TOR.

ROBERT H. ANDERSON ll I.

E R O L B 8 M A H m E H C R O H m AT TORNE Y Oct. 26, 1965 Filed Aug. 6,1962 United States Patent 3,214,631 TUBE HAVING TARGET WITH STORE AND/OR NON-STORE SECTIONS Robert H. Anderson, Portland, Oreg., assignor toTektronix, Inc., Beaverton, 0reg., a corporation of Oregon Filed Aug. 6,1962, Ser. No. 214,877 17 Claims. (Cl. 315-12 The subject matter of thepresent invention relates generally to cathode ray storage tubes, and inparticular to direct viewing bistable storage tubes which employ a thinintegral layer of secondary emissive phosphor material as the storagedielectric of the storage target in such tubes. The phosphor layer has athickness within a critical range of thicknesses over which the phosphormaterial can function both to store a bistable electrical charge imagefor an indefinite controllable time and to emit a visible light imagecorresponding to such charge image. The storage target of the presentinvention also employs a coating of light transparent electricallyconductive material beneath the phosphor layer to apply target voltagesthereto. In addition the integral phosphor layer is provided with asufliciently porous structure to enable the transmission of secondaryelectrons through such layer which are emitted from one side of thephosphor layer and are collected by the conductive coating targetelectrode on the opposite side of such layer, as described in mycopending U.S. patent application, Serial No. 180,457, hereafterreferred to.

In order to enable the phosphor layer of the storage target to store abistable charge image, the target voltage applied to the conductivecoating must be within a stable range of voltages. This stable range'isbetween a lower limit retention threshold voltage below which storage isnot possible, and an upperlimit fade positive voltage" above which theflood electrons, normally used to maintain the charge image produced bya writing beam, produce a uniform charge over the target dielectric sothat a charge image is not possible. The conductive coating is separatedinto a plurality of spaced conductive areas which may be connected todifferent potentials in order to provide a split screen storage targetso that some portions of the phosphor layer over such areas will store,and other portions will not store a charge image. Thus one portion ofthe storage target may be used for merely viewing an electrical signalapplied to the storage tube without storing such signal, while anotherportion of such target may be used to view and store the image of thisor another signal. In this manner several different signal waveforms maybe stored side by side for comparison purposes without the danger ofobscuring the waveform traces. Still other portions of the storagetarget over different conductive areas may be employed to displaycharacters which correspond to different positions of switches whichcontrol the operation of such storage tube, for example, the verticalgain and the horizontal sweep speed switches of a cathode rayoscilloscope.

The storage tube of the present invention is especially useful in acathode ray oscilloscope to display and store the waveforms ofelectrical signals received by such oscilloscope. However, the newstorage tube may also be employed as part of a sonar or radarinstallation, an electronic computer or other apparatus which ordinarilyemploys a storage tube. Since the storage tube of the present inventionis an improvement over the tube described by the same inventor incopending US. patent application Serial No. 180,457 filed on March 19,1962, by Robert H. Anderson, and entitled Electron Discharge DisplayDevice, the disclosure of this copending application is herebyincorporated into the present application in order to avoid unnecessaryduplication. The present storage tube has several advantages over theprevious storage tube since it employs a storage target which isconstructed to enable portions of the target to operate in a bistablestorage mode while other portions of such target operate in a nonstoragemode. This allows a portion of the target to be employed as a previewingarea for the electrical signal under investigation, while another targetportion can be employed as a storage area so that adjustment errors invertical gain, horizontal sweep speed, or triggering can be corrected bydisplaying the trace in the previewing area before moving it to thestorage area. This previewing eliminates the necessity for erasing thestored image of an incorrect trace which would be caused by such anadjustment error. The split screen storage target also allows two ormore traces to be stored side by side for comparison without danger ofobscuring the traces due to one incorrect trace, which can save muchtime ordinarily lost due to repeated erasing of the storage target or torepeated assembly and disassembly of the different arrangements of theapparatus under test.

Another advantage of the present storage tube is the construction ofseparate target areas as a character display which may be used tovisually indicate directly on the storage target the positions ofswitches employed to control the operation of the storage tube. Theswitch position character display is located at the outer edge of thestorage target so that photographs of waveforms presented on the storagetarget are automatically labeled as to the control voltage and timeunits for the vertical and horizontal axes, respectively, of thegraticule scale on the face plate of such tube. A further advantage ofdisplaying the switch positions directly on the storage target is thatthey may be viewed at the same time as the signal waveform, therebyeliminating the need for movement of the observers eyes from the viewingscreen of the storage tube to the control switches to determine thegraticule scale units.

Still another advantage of the storage tube of the present invention isthat it employs an envelope having a ceramic funnel portion which isprovided with a plurality of spaced ridges on the outer surface thereofextending from a point adjacent the larger end of such funnel portionwhich is sealed to the glass face plate portion of such envelope, to apoint remote from such face plate where the funnel portion is of reduceddiameter. Conductive lead strips are provided over the tops of theridges on the exterior of the envelope, which are electrically connectedto different conductive areas of the storagev target and to variousconductive wall coatings on the inner surface of the funnel envelopeportion inside such envelope. A connector socket in the shape of acollar sleeve is provided around the small end of such funnel envelopeportion so that spring contacts in such socket engage the lead strips toconnect the electrodes attached to such strips to different voltagesources connected to such contacts. This allows a large number ofelectrical connections to be made in the region of the face plate, suchas would be necessary if a switch position character display is employedas part of the target, without increasing substantially the spaceoccupied by the storage tube.

It is therefore one object of the present invention to provide animproved cathode ray storage tube.

A further object of the invention is to provide an improved storage tubewhich is capable of producing a storage display and a nonstorage displaysimultaneously.

Another object of the invention is to provide an improved direct viewingstorage tube of the type having a storage target which also functions asthe viewing screen of such tube and in which the storage target isdivided into a plurality of separate independent target areas which canbe employed either as storage or nonstorage areas to provide both astorage display and a nonstorage display simultaneously on the sametarget.

A still further object of the invention is to provide an improvedstorage tube which is capable of producing both a character display anda signal display simultaneously.

Still another object of the present invention is to provide an improveddirect viewing, bistable storage tube which has a character display areaon its storage target for indicating positions of controls employed tovary the vertical gain, horizontal sweep speed or other characteristicsof such storage tube.

An additional object of the present invention is to provide an improvedstorage target in which a thin dielectric layer of secondary emissivephosphor material is employed to store an electrical charge image and toemit a visible light image corresponding to such charge image, and inwhich a light transparent coating of electrically conductive materialpositioned beneath such dielectric layer is employed as a plurality ofindependently controlled target electrodes by separating such coatinginto a plurality of spaced conducting areas which may be connected todifferent target voltages in order to enable the portions of suchdielectric layer above such conducting areas to store a charge image foran indefinite controllable time or to operate in a nonstorage mannerdepending upon the magnitude of such target voltages.

Another object of the present invention is to provide an improvedstorage tube in which an envelope having a ceramic funnel portion with aplurality of conductively coated of spaced ridges on the exteriorsurface of such funnel portion is employed along with a connector socketcollar to electrically connect a plurality of separate conductive areason the storage target and wall coatings inside such tube to voltagesources outside the tube.

Other objects and advantages of the storage tube of the presentinvention will be apparent in the following detailed description of apreferred embodiment thereof and in the attached drawings of which:

FIG. 1 is a side view of one embodiment of the storage tube of thepresent invention with parts broken away to show internal structure;

FIG. 2 is a front view of the storage tube of FIG. 1;

FIG. 3 is a vertical section view taken along the line 33 of FIG. 1 withparts broken away to show the internal structure of the storage target;

FIG. 4 is a partial vertical section view taken along the line 4-4 ofFIG. 3;

FIG. 5 is an enlarged view of a corner of the character display portionof one embodiment of the storage target of the present invention withparts broken away to show internal structure;

FIG. 6 is a partial vertical section view taken along the line 6-6 ofFIG. 5;

FIG. 7 is an enlarged view of part of another embodiment of the storagetarget of the present invention;

FIG. 8 is an oblique vertical section view taken along the line 88 ofFIG. 7;

FIG. 9 is an oblique sectional view similar to FIG. 8 showing a thirdembodiment of the storage target of the present invention; and

FIG. 10 is an oblique sectional view similar to FIG. 8 showing a fourthembodiment of the storage target of the present invention.

One embodiment of the storage tube of the present invention is shown inFIG. 1 to include, briefly, a storage target 10 supported on the innersurface of a light transparent face plate 12 of glass material which issealed to the large end of a hollow, funnel shaped envelope portion 14of ceramic material to form part of the envelope of such storage tube.The ceramic funnel portion 14 may be sealed at its small end to a hollowtubular neck portion 16 of glass material which contains the electrongun structure of the writing gun 17 and the flood guns 18 disclosed inmy copending US. patent application Serial No. 180,457 previouslyreferred to. The electrostatic deflection plates of the writing gun 17as well as the isolation shield between such deflection plates may beconnected to conventional vertical amplifier, horizontal sweep generatorand high voltage supply circuits (not shown) by means of metal lead pins19 extending through the side of the neck portion 16 of the envelope.The remaining gun structure of the writing gun 17 and the flood guns 18may be connected by means of lead pins 20 extending through the rear endof such neck portion and held in proper spaced relationship by a plug 22of insulating material. The writing gun produces a narrow beam of highvelocity electrons which is moved across the storage target inaccordance with an input signal applied to the vertical deflectionplates of such writing gun to produce a charge image on such target.This charge image is stored or maintained by the low velocity electronsemitted by the flood guns which are substantially uniformly distributedover the storage target.

As shown in FIGS. 2, 3 and 4, the storage target 10 of the presentinvention differs from the storage target of the previously referred toapplication in that the light transparent coating of conductivematerial, such as tin oxide, employed in such target is divided into aplurality of separate conductive areas 24, 26, and 28. These conductiveareas are coated over the inner surface of the glass face plate 12 andare separated by horizontal gaps and 32 in the conductive coating. Asecondary emissive dielectric layer 34 of phosphor material, such as P-ltype phosphor, is provided over the conductive areas 24, 26 and 28 onthe face plate 12 by a decalcomania technique. This is an integralsemicontinuous phosphor layer 34 which has a sufliciently porousstructure to enable the transmission of secondary electrons through suchlayer for collection by the conductive areas, and a thickness that iswithin a critical range of thicknesses over which the particularphosphor material employed is capable of storing a bistable electricalcharge image for an indefinite controllable time in the manner disclosedin my above mentioned copending application. Thus the phosphor layer 34serves two primary functions-first, to store the electrical charge imageproduced by the writing gun 17 and maintained by the flood guns 18 ofthe storage tube; and second, to emit a visible light imagecorresponding to such charge image so that an optical readout isobtained from the storage tube. It should be noted here that the storagetube of the present invention, along with my previous storage tube, isalso capable of electrical readout since an output signal is obtainedfrom the conductive areas 24, 26 and 28 when a reading beam is movedacross the charged surface of phosphor layer 34. Thus if the conductiveareas are electrically connected to the Z-axis input of a TV monitortube and the raster signal of such TV monitor is transmitted to thedeflection plates of the writing gun during electrical readout, anelectrical readout signal corresponding to the stored charge imageincluding the character display mentioned above, can be reproduced onthe TV monitor or other electrical display device since such writing guncan also be employed as the reading gun of the storage tube if desired.

An edge lighted graticule scale 36 may be provided on the inner surfaceof the flat glass face plate 12 either in the form of the scribed linesshown in FIG. 4, or as glass frit lines which are deposited on the innersurface of such face plate and fused thereto. While any scale can beemployed, the graticule scale 36 shown is made up of vertical andhorizontal lines which divide up the viewing area over the conductingareas 24, 26 and 28 into one centimeter squares to form a scale having arectangular shape of 8 centimeters by 10 centimeters which has itshorizontal axis centered over gap 30.

Since the target voltages on the conductive areas 24 and 26 determinewhether the portions of the phosphor layer 34 overlying such conductiveareas operate in a storage mode or a non-storage mode, one portion ofthe phosphor layer can be employed as a conventional fluorescent viewingscreen for producing a visual image of the electric signal waveformunder investigation without storing such image, while the other portionof phosphor layer can be used as a storage dielectric for storing theimage. This allows the waveform to be previewed by the operator on oneportion of the storage target before it is stored on another portion ofsuch target. Connecting one of the conductive areas 24 and 26 to avoltage that is within the stable range of target voltages causes thatportion of the phosphor layer over such one conductive area to store acharge image for an indefinite controllable time, while connecting theother area to a voltage below the retention threshold voltage of suchlayer prevents that portion of the layer over such other area fromstoring such a charge image. Thus, the use of two separate conductiveareas 24 and 26, rather than one, allows a portion of the storage targetto operate in the storage mode and another portion of such target tooperate in a nonstorage mode merely by properly selecting the targetvoltages applied to such conductive areas. This split screen storagetarget is of great convenience when comparing two different signalwaveforms side by side since errors in vertical gain, horizontal sweepspeed or sweep triggering can be corrected before storage by previewingthe waveform on the non-storage target area and then moving suchwaveform to the storage area by adjustment of the vertical positioncontrol. The vertical position control may be provided with a scalewhich is calibrated in terms of the horizontal graticule lines in orderto allow more exact location of the stored image on the storage area ofthe target.

The electrical connections to the conductive areas 24, 26 and 28 may beaccomplished by extending their conductive coatings of tin oxide up tothe edge of the glass face plate 12 so that they extend through theglass frit seal 38 connecting such face plate to the ceramic funnelportion 14, as shown in FIG. 4. This funnel portion of the tube envelopemay be provided with a plurality of spaced ridges 40 which extendlongitudinally from a point adjacent the face plate at the large end ofsuch funnel back toward the neck portion 16 to a point near the smallend of such funnel portion. Each of these ridges 40 may be provided witha fired lead strip 42 of conductive material, such as silver, whichextends along the top of such ridges and is connected by a conductorcoating 43 with the lead portions of the conducting areas 24, 26 and 28that extend through the glass seal 38. The metal lead strips 42 can beapplied to the top of the ridges 40 before sealing the ceramic funnel 14to the glass face plate 12 by rolling a roller coated with silver paintover such ridges, or the lead strips may be painted in the groovesbetween the ridges if it is desired. After sealing, the conductorcoating 43 is applied over the glass seal 38 to electrically connect thelead strips 42 to the conductive areas. Of course, if all of the ridgesare not used as supports for lead strips, as is true of the embodimentshown, the unused ridges may be covered with a suitable masking materialbefore the lead strips are applied to the remaining ridges.

The inner surface of the funnel portion 14 of the envelope may beprovided with a plurality of axially spaced wall coatings 44, 46, 48 and50 of conductive material, such as silver, which function as focusing,collimating and collecting electrodes for the primary electrons emittedby the writing gun 17 and the flood guns 18 and for the secondaryelectrons emitted by the storage target 10. Each of these wall coatingsmay be connected to the exterior of the funnel portion of the envelopeby a hole through the side of such funnel portion. The inner surface ofthe hole is coated with a connector layer 52 of conductive material,such as silver paint, and then the hole is filled by a plug 54 of glassfrit material, as shown in FIG. 3. The connector layer 52 is continuedover the top of the glass plug 54 up the side of the adjacent ceramicridge 40 into contact with the lead strip 42 on the top of such ridge inorder to complete the electrical connection of the wall coating to theexterior of the envelope. The first wall coating 50 nearest the storagetarget 10 is spaced from the phosphor layer 34 and the second wallcoating 48 by narrow gaps to electrically insulate such first wallcoating from these two elements. In order to obtain more uniformbackground illumination of the storage target, the first wall coating 50may be split into four separate portions 56, 58, 60 and 62 which areseparated with four spacer gaps adjacent the ends of gaps 30 and 32between the conductive areas 24, 26 and 28, and the wall coatingportions are each connected by dilferent connector layers 52 and leadstrips 42 to an external voltage source for independently controllingthe voltages applied thereto in a manner hereafter described.

The lead strips 42 are connected to different voltage sources by meansof a connector socket 64 shown in FIG. 1 which consists of a hollowfrustro-conical sleeve 66 of insulating material which fits as a collararound the small end of the funnel portion 14 of the envelope. Aplurality of leaf spring contacts 68 are attached at circumferentiallyspaced points on the inner surface of the collar sleeve 66 so that eachof such spring contacts extends radially inward into engagement with oneof a plurality of notches 70 in the end of the envelope ridges 40adjacent neck envelope portion 16. The spring contacts 68 are fastenedto the collar sleeve 66 by metal eyelet rivets 72 which may be solderedto lead wires 74 that are electrically connected to different voltagesources. Thus the spring contacts 68 electrically connect the leadstrips 42 to the voltage sources in order to apply different voltages tothe wall coatings and to the conductive target areas of the storagetube. The collar sleeve 66 of the connector socket 64 may be providedwith annular flanges 75 and 76 which extend inwardly from the oppositeends of such sleeve to serve as stops to limit axial movement of suchconnector socket in a direction toward the face plate 12. The smallerdiameter flange 76 must have an opening large enough to clear the leadpins 18 when such connector socket is moved over the neck portion of theenvelope into its proper position. A keyway (not shown) may be providedin larger diameter flange 75 of the collar sleeve 66, which engages oneof the ridges 40 to prevent rotation of the connector socket after it isproperly positioned.

The storage target 10 of the present invention may also have a characterdisplay structure that may include a vertical gain display 77 and ahorizontal sweep speed display 78 which enable the switch positions ofthe controls employed to vary the vertical gain and horizontal sweepspeed, respectively, of the storage tube to be displayed directly on thestorage target within the graticule scale 36 so that they areautomatically recorded in photographs of the graticule area of thetarget. These character displays 77 and 78 may include a plurality ofnumbers, letters and other symbols which are formed by providingseparate independent storage areas for each character. This isaccomplished in one embodiment of the storage target shown in FIGS. 3, 5and 6 by separating the conductive coating area 28 into a plurality ofspaced areas 76 which are shaped in the form of the characters to bedisplayed. Each of these character areas 76 includes a lead portionwhich extends through the glass seal 38 to the edge of the face plate 12into electrical contact with a conductor layer 43 and a lead strip 42 onone of the ridges 40. i

In order to prevent that portion of the phosphor layer 34- whichoverlies the lead portion of the character areas 76 from storing andproducing a light image of the lead, a lead cover layer 79 of dielectricmaterial is provided over the lead portions of the character areas. Asshown in FIG. 6, the lead cover layer increases the total thickness ofthe target dielectric over the lead portion of the character area 76 sothat it is greater than that of the remaining phosphor storagedielectric over such character area. This allows the retention thresholdvoltage of the thicker dielectric region to be above the fade positivevoltage of the thinner phosphor region so that a voltage may be appliedto the conductive character area 76, which makes the thinner region fadepositive to a uniformly illuminated condition to light the character andallows the thicker region to remain negative in an unwritten or darkcondition to prevent the lead portion from lighting up. The lead coverlayer 79 may be P1 type phosphor material similar to that of thephosphor layer 34 so that it may be provided merely as a thickenedportion of such phosphor layer if desired. Another way of covering thelead portions of the character areas 76 to prevent the light image ofsuch lead areas from being seen would be to provide a masking layer oflight opaque material as the lead cover layer 79. This would not preventthe portion of the phosphor layer 34 over the lead cover layer fromlighting up but would prevent the light image of the lead from beingtransmitted through the face plate.

If the phosphor layer 34 is about .0015 inch thick, it will have aretention threshold voltage of about +250 volts DC. and a fade positivevoltage of approximately +350 volts DC. with respect to the flood guncathode. Therefore, when the character area 76 is switched to a voltagegreater than +350 volts that portion of the phosphor layer 34 about thecharacter area will immediately change into a written storage conditionin which the entire portion of the phosphor layer is illuminated in thecharacter shape of the underlying conductive area. However, if the leadcover layer 78 is P-l phosphor, .001 inch thick, the total thickness ofthe phosphor region above the lead portion of the conductive characterarea 76 is .00l5+.00l or about .0025 inch. This thicker phosphor regionwill have a retention threshold voltage of about +450 volts D0. whichmust be exceeded before storage is possible in this region. Therefore,if the character area 76 is maintained at a voltage between +350 and+450 volts, such as +400 volts, the character region of the overlyingphosphor layer will be illuminated while the lead region of suchphosphor layer will remain in a dark or unilluminated condition. Sincethe retention threshold voltage of the phosphor layer 34 is about +250volts when such layer is .0015 inch thick, some of the characters in thedisplays 77 and 78 can be illuminated by merely switching such characterareas 76 to +400 volts, while connecting the other characters to avoltage below +250 volts. For example, if the characters 50 v./cm. ofthe character display 77 and the characters .2 a sec./ cm. of thecharacter display 78 are illuminated, the voltage gain switch is set at50 volts per centimeter uncalibrated and the sweep speed switch is setat .2 microsecond per centimeter calibrated.

In order to achieve the most desirable results the background or darkvoltage on the character areas which are not to be illuminated, is setto some intermediate voltage between 0 and +250 volts, for example about+145 volts, rather than merely being reduced to 0. This dark voltageprevent a large negative charge from accumulating on regions of thephosphor layer which are adjacent the character regions desired to beilluminated, thereby overcoming a coplanar grid elfect caused by thenegatively charged phosphor regions which would deflect the floodelectrons inward at the edges of the character areas and cause thecharacter image to be distorted and unevenly illuminated. This coplanargrid effect is also apparent between the phosphor region over conductivearea 26 and the top of the characters. In order to Overcome this defect,a guard band 80 of tin oxide is provided around the character displays77 and 78 as a separate part of the conductive area 28. .The guard bandis spaced from and shaped to conform to the top of the character areas76 and is also spaced from the bottom conductive area 26 by gap 32. Aportion of the guard band 80 extends between the voltage gain characterdisplay 77 and the sweep speed character display 78 to the edge of theface plate 12 into electrical contact with one of the lead strips 42 onthe ridges 40 at the bottom of such face plate. In a similar manner tothe dark or unilluminated character areas, the guard band is connectedto a dark voltage of about volts D.C. in order to insure uniformillumination of the selected characters.

Another effect similar to the coplanar grid effect is also observed onthe portions of the phosphor layer 34 overlying the corners of theconductive areas 24 and 26 adjacent the gap 30 when the first wallcoating 50 is provided as one continuous coating. Thus, if targetportion corresponding to the conductive area 26 is operated in a storagecondition, while that corresponding to the conductive area 24 isoperated in a non-storage condition, the phosphor region over the upperconductive layer 24 becomes more negatively charged than the phosphorregion over the lower conductive area 26. This together with the +50volts D.C. potential on the wall coating 50 causes the flood electronsdirected at the upper corners of the conductive area 26 to be deflecteddownward so that the phosphor over these corners has a lower backgroundillumination than the remainder of the phosphor layer overlying suchconductive area. This non-uniform illumination can be corrected bysplitting the first wall coating 50 into the four parts 56, 58, 60 and62 and raising the potential of the wall coating part 56 which isadjacent the upper conductive area 26 to volts, while maintaining thevoltage of wall coating portions 58 and 62 adjacent the lower conductivearea at +50 volts. The same effect is present to a lesser extent at thelower corners of the conductive area 26 since they are adjacent theguard band 80 and the phosphor layer overlying such guard band isnegatively charged in a similar manner to the conductive area 24. Thusthe wall coating portion 60 surrounding such guard band may be providedwith an operating potential which isadjustable over the range of 0 to+150 volts D.C.

Another embodiment of the character display portion of the storagetarget is shown in FIGS. 7 and 8 to include tin oxide character areas 82which are similar to character areas 76 except that they are not formedin the shape of the characters, but may be of the generally rectangularshape shown in dotted lines. As shown in FIG. 8, an intermediatephosphor layer 84 is provided over the surface of the character areas 82before the phosphor layer 34 is applied. This intermediate phosphorlayer 84 is provided with character shaped holes which are positioned tofall on the character areas 82. As a result the second phosphor layer 34is depressed into the character shaped holes of the intermediatephosphor layer 84 so that the total thickness of the phosphor is less insuch holes than it is in the surrounding background regions. Theintermediate phosphor layer 84 can also be extended down over the leadportion of the conductive character areas 82 so that it replaces thelead cover layer 79 of FIG. 6. Therefore, if the intermediate phosphorlayer 84 is about .001 inch thick, the same thickness as the lead coverlayer 79, only that portion of the phosphor layer 34 which is depressedinto the character shaped holes in the intermediate layer will beilluminated when the conductive area is connected to +400 volts DC. Thereason for this is that the thicker background region has a retentionthreshold voltage of +450 volts since it is the same thickness as thatof the phosphor region over the lead cover layer 79 previously referredto.

A third embodiment of the character display portion of the storagetarget 10 is shown in FIG. 9 to be similar to that shown in FIGS. 7 and8 except that the intermediate phosphor layer 84 is replaced with alight opaque masking layer 86 having character shaped holes over theconductive character areas 82. The masking layer 86 may be any lightopaque material such as aluminum, silver or other suitable metals, or awhite ceramic powder which can be fused either directly to the glassface plate 12 or over the conductive areas 82 and has an advantage overmetal in that it is substantially invisible when viewing on a backgroundof P-l phosphor. Here the thickness of the masking layer 86 is notimportant except to the extent that it is opaque. While the entirephosphor region over the character area 82 may be charged to a storagecondition and illuminated, the only light transmitted through the glassface plate 12 is that which passes through the character shaped holes inthe masking layer 86. Thus only the character image is visible from thefront end of the storage tube.

A fourth embodiment of the display portion of the storage target isshown in FIG. 10 to include a glass layer 88 having character shapedholes therein, which extends over the upper portion of the conductivecharacter areas 82, but not over the lead portion of such characterareas. This glass layer may be powdered glass frit which is fused to theface plate 12 over the conductive areas 82. The character shaped holesin the glass layer 88 are filled with phosphor material to the samethickness as the glass layer, for example, by the use of a squeegee tospread a solution of the phosphor material over such glass layer. Inthis embodiment the phosphor layer forming the signal display portion ofthe storage target may be terminated below the conductive area 26 beforeit covers the glass layer 88 so that such phosphor layer 34 would notextend over the lead portion of the character areas 82. Of course, thenthere would be no problem as far as unwanted illumination of thecharacter leads because the phosphor material over the leads has beenremoved.

While the conductive target coating has been shown to be split into twoequal signal display areas 24 and 26, it is obvious that theseconductive areas may be of different dimensions. Thus if it is desirableto store several traces on the bottom area 26, this area may be madetwice as wide as the top area 24 which could be then used as a previewarea for observing the signal waveforms before storage. If this weredone, the vertical position knob of the cathode ray oscilloscope couldbe provided with a scale calibrated in accordance with the graticulescale, as discussed previously, for moving waveform trace from thepreviewing area 24 to the exact position desired on the storage area 26.Another modification of the storage target of the present inventioncould be made by providing a large plurality of horizontal strips ofconductive material in place of the two conductive areas 24 and 26. Theelectrical leads to these strips could then be connected to a suitableselector switch on the front panel of the oscilloscope in order tointerconnect any number of strips into different sized groups. Thiswould allow the position of the nonstorage area and the storage area tovary as well as the size of such target areas. For example, if sixteenstrips were employed, the top six strips could be connected to +300volts to function as a first storage area, the next four strips could beconnected to +100 volts to function as a hon-storage area, and thebottom. six could be connected to +300 volts to function as a secondstorage area. The selector switch could also be calibrated in terms ofeither the horizontal graticule lines or in terms of the number ofstrips employed in order to accurately position the location of the gapor split between storage and nonstorage areas.

Of course all the signal display areas of the target includingconductive areas 24 and 26 may be operated in a storage mode or anon-storage mode, rather than having both storage areas and non-storageareas. When target areas 24 and 26 are operated as storage areas, eachmay be erased independently of the other by raising the target voltageabove the fade positive voltage and then lowering it below the retentionthreshold voltage in the manner disclosed in the patent applicationreferred to above. This allows several different signal waveforms to bestored and erased successively for comparison with the same standardwaveform which is stored on another target area.

In addition to the uses already described, the split screen storagetarget of the present invention can be employed to clip a signalwaveform above or below a selected voltage magnitude by positioning suchwaveforms over the gap between adjacent storage and non-storage targetareas, with the quiescent voltage trace a predetermined verticaldistance from such gap which corresponds to such voltage magnitude.Thus, that portion of the waveform which is above or below the selectedvoltage, depending on the type of clipping employed, is positioned onthe non-storage target area so that it is not stored. This wouldindicate which portion of the waveform is transmitted or rejected by theparticular clipping circuit under investigation. It should be noted thatit is possible that the waveform image may be lost when storing signalsof very low amplitude if such waveform is positioned exactly in the gap30 between the conductive areas 24 and 26 when the gap is in the form ofa horizontal line. This can be avoided if the gap is in the form of azigzag or sawtooth line.

In order to avoid the coplanar grid effect mentioned above, theconductive areas on the glass face plate 12 should be positioned closetogether in order to cover as much glass surface as possible to preventa high negative charge from accumulating on such uncovered glasssurface. Also the conductive areas of all non-storage regions of thetarget should be connected to a dark voltage in the neighborhood ofvolts D.C. rather than to 0 volts to avoid this effect. Since a thickphosphor layer of storage dielectric has a tendency to accumulate moreof a negative charge than a thin phosphor layer, it may be necessary toprovide a separate thin layer of phosphor over the character areas if arelatively thick layer of phosphor is employed over the conductive areas24 and 26, to prevent the coplanar grid effect from blurring thecharacter display. It should be noted that while the two characterdisplays 77 and 78 indicated in FIG. 2 are those of the vertical gainand horizontal sweep speed, respectively, of the oscilloscope, othercharacter displays may also be employed. In addition to the twocharacter displays 77 and 78 another pair of character displayscorresponding to the character displays shown, may be positioned alongthe top of the face plate 12 above the conductive area 26 if the storagetube is suitably modified so that it can be used in a dual trace or adual beam type oscilloscope. This second pair of character displayswould indicate the vertical gain and the horizontal sweep speed of thesecond input signal applied to the storage tube. Of course either thesplit screen portion of the storage target including conductive coatingareas 24 and 26, or the character display portion of the storage targetcan be employed together or separately in the storage tube of mypreviously filed patent application, Serial No. 180,457.

Itwill be obvious to those having ordinary skill in the art that variouschanges may be made in the details of the above described preferredembodiment of the present invention without departing from the spirit ofthe invention. Therefore it is not intended to limit the scope of thepresent invention to the details of the preferred embodiment thereof andthat scope should only be determined by the following claims.

I claim:

1. A direct viewing storage target for use in a cathode ray storagetube, comprising:

a support member of insulative material;

a first electrically conductive area on one portion of the surface ofone side of said support member;

a second electrically conductive area on another portion of said surfaceof said support member and insulatingly spaced from said first area; and

a storage dielectric layer of phosphor maten'al supported on said oneside of said support member over said first area and said second area,said dielectric layer being an integral layer of sufficiently porousstructure to enable secondary electrons emitted from one side of thelayer to be transmitted through said layer and collected by saidconductor areas on the opposite side thereof so that said phosphormaterial can store an electrical charge image for an unlimited time overa stable range of target voltages applied to said first and secondconductive areas, and will emit a light image corresponding to saidcharge image, when bombarded by electrons.

2. A direct viewing storage target for use in a cathode ray storagetube, comprising:

a support member of light transparent insulative material;

.a first light transparent film of electrically conductive materialcoated over one portion of the surface of one side of said supportmember;

a second light transparent film of electrically conductive materialcoated over another portion of said surface of said support member sothat it is insulatingly spaced from said first film;

a storage dielectric layer of phosphor material supported on said oneside of said support member over said first film and said second film,said dielectric layer being an integral layer of sufficiently porousstructure to enable secondary electrons emitted from one side of thelayer to be transmitted through said layer and collected by saidconductive film on the opposite side thereof so that said phosphormaterial can store an electrical charge image for an indefinite, controllable time over a stable range of target voltages applied to saidfirst and second films, and will emit a light image corresponding tosaid charge image, when bombarded by electrons; and

means for applying a different target voltage to said first film than tosaid second film to allow one of these films to have a target voltagewhich is within said stable range and the other film to have a targetvoltage which is outside said stable range during the time charge imagesare formed on the portions of the dielectric over said films, so thatthe portion of said dielectric layer above said one film will store acharge image and the portion of said dielectric layer above said otherfilm will not store a charge image.

3. A direct viewing bistable storage target for use in a cathode raystorage tube, comprising:

a support member of light transparent insulative material;

a first light transparent film of electrically conductive materialcoated over one portion of the surface of one side said support member;

a second light transparent film of electrically conductive materialcoated over another portion of said surface of said support member sothat it is insulatingly spaced from said first film;

a dielectric layer of phosphor material supported on said one side ofsaid support member over said first film and said second film, saiddielectric layer being semicontinuous and having a substantially uniformthickness that is within the range of thicknesses over which saidphosphor material can store a bistable electrical charge image for anindefinite controllable time over a stable range of target voltagesapplied to said first and second films, and will emit a light imagecorresponding to said charge image, when bombarded by electrons; and

means for applying a different target voltage to said first film than tosaid second film to allow one of these films to have a target voltagewhich is within said stable range and the other film to have a targetvoltage which is outside said stable range during the formation ofcharge images on the portions of the dielectric layer over said films,so that the portion of said dielectric layer above said one film willstore a charge image and the portion of said dielectric layer above saidother film will not store a charge image. 4. A direct viewing bistablestorage target for use in a cathode ray storage tube, comprising:

a support member of light transparent glass insulative material;

a graticule scale provided on the surface of one side of said supportmember;

a first light transparent layer of tin oxide conductive material coatedover said graticule scale on one portion of the surface of said one sideof said support member;

a second light transparent layer of tin oxide conductive material coatedover said graticule scale on another portion of the surface of said oneside of said support member and insulatingly spaced from said firstlayer;

a dielectric layer of phosphor material supported on said one side ofsaid support member over said first layer and said second layer, saiddielectric layer being semicontinuous and having a substantially uniformthickness that is within the range of thicknesses over which saidphosphor material can store a bistable electrical charge image for anindefinite, controllable time over a stable range of target voltages onsaid first and second films, and will emit a light image correspondingto said charge image, when bombarded by electrons; and

means for applying different target voltages to said first and secondlayers to allow one of these conductive layers to have a target voltagewhich is within said stable range and the other conductive layer to havea target voltage which is outside said stable range during the formationof charge images on the portions of said dielectric layer over saidconductive layers, so that the portion of said dielectric layer abovesaid one conductive layer will store a charge image and the portion ofsaid dielectric layer above said other conductive layer will not store acharge image in order to allow previewing on said storage target of anelectrical signal applied to said storage tube before the image of saidsignal is stored on said storage target.

5. A viewing screen for use in a cathode ray tube which produces acharacter display on one portion of said screen, comprising:

a light transparent support member;

a plurality of spaced light transparent areas of electrically conductivematerial secured to one side of said support member in spaced, insulatedrelationship to each other;

a dielectric layer of phosphor material supported on said one side ofsaid support member with a first portion remote from said conductiveareas and a second portion over said conductive areas;

means supported by said support member, for causing the second portionof said dielectric layer to form a light image in the shape of acharacter over each of said conductive areas when the proper voltage isapplied to said conductive areas; and

means for app-lying different voltages to said conductive areas.

6. A direct viewing bistable storage target for use in a storage tubewhich indicates the position of switches for controlling the operationof said storage tube, comprising:

a support member of light transparent insulative material;

a light transparent layer of electrically conductive material secured toone side of said support member;

a plurality of spaced light transparent areas of electrically conductivematerial secured to said one side of said support member in spaced,insulated relationship to each other and to said conductive layer;

a dielectric layer of phosphor material supported as a semicontinuouslayer on said one side of said support member with a first portion oversaid conductive layer and a second portion over said conductive areas,said first portion of said dielectric layer having a sutficiently porousstructure to enable the transmission of secondary electrons through thedielectric layer to said conductive layer so that said phosphor materialcan store a bistable electrical charge image for an indefinitecontrollable time over :a stable range of target voltages applied tosaid conductive layer and will emit a light image corresponding to saidcharge image, when bombarded by electrons;

means for causing the second portion of said dielectric layer to form alight image in the shape of a character over each of said conductiveareas which correspond to the position of said switch when the propervoltage is applied to said conductive areas; and

means for applying different voltages to said conductive areas and saidconductive layer.

7. A direct viewing bistable storage target for use in a a dielectriclayer of phosphor material supported on said one side of said supportmember with a first portion over said conductive layers and a secondportion over said guard band and said conductive areas, said firstportion of dielectric layer having a substantially uniform thickness andat least some parts of said second portion of said dielectric layerhaving a thickness, which are within the range of thicknesses over whichsaid phosphor material can store an electrical charge image for anindefinite controllable time over a stable range of collector voltagesapplied to said conductive layer and said conductive areas, and willemit a light image corresponding to said charge image, when bombarded byelectrons; and

means for applying different collector voltages to said conductiveareas, said conductive layers and said guard band.

9. A cathode ray tube, comprising:

an envelope of insulating material having a light transstorage tubewhich indicates the position of switches in a cathode ray oscilloscopeemploying said storage tube, comprising:

parent face plate portion secured to a funnel portion; a viewing screenincluding a plurality of spaced, light transparent areas of conductivematerial secured to a support member of light transparent insulativematerial; .a light transparent layer of electrically conductive mateaportion of the inner surface of said face plate in spaced insulatedrelationship, and a dielectric layer of phosphor material supported onsaid inner surface of rial secured to one side of said support memb r;said face plate with a first portion remote from said a plurality ofspaced light transparent areas f l conductive areas and a second portionover said concally Conductive material formed in the shape of ductiveareas, and means for causing said portion of charaoters which correspondto different switch P said dielectric layer to form a light image in theshape tions and secured to said one side of said pp of a character overeach of said conductive areas member in spaced, insulated relationshipto each other h th proper Voltage i applied t aid conductive and to saidconductive layer; areas;

a dielectric layer of P p material supported on a plurality of spacedconductive leads coated on the exsaid one side of said pp member with afirst P terior of the funnel portion of said envelope with a n oVer saidConductive layer and a Second Portion difierent lead being electricallyconnected to each ever said Conductive areas, said first Portion of saidone of said conductive areas inside said envelope; dielectric layerhaving a substantially uniform thickmeans for l i diff t Voltages t eachf said ness and at least some parts of said second portion l d of saiddielectric layer having a thickness, which is means for generating abeam of high velocity electrons within the range of thicknesses Overwhich said P and for deflecting said beam across the dielectric Pmaterial can Store an electrical charge image layer of said viewingscreen in response to an elecfor an indefinite controllable time withina stable trical Signal to for an image f i i l on id range of targetvoltages on said conductive layer and di l i 1 d d Conductive and willemit a light image means for bombarding said dielectric layer with lowcorresponding to said charge image, when bombarded 4 velocity electronsto produce said character images. y electrons; and 10. A direct viewingstorage tube, comprising:

means for pp y different Voltages to said conductive an envelope ofinsulating material having a light transareas and to said conductivelayer so that the voltage parent f e plate portion secured to a f lportion; on som f a Conductive areas can be below said a storage targetincluding a light transparent layer of stable range and the voltage onother of Said areas conductive material and a plurality of spaced, lighta be above said Stdhie range in order to form a light transparent areasof conductive material formed in image in the Shape of said other areason Said Second the shape of different characters, which are securedportion of said dielectric layer to indicate the position to h inner facof said face plate in spaced of said switches. insulated relationship,and a storage dielectric layer 8. A direct viewing storage target foruse in a storage of phosphor material supported on said inner tube toindicate the position of switches in a cathode ray f f said fa plateover id conductive layer OSCiiIOSCOPe p y g said storage tube,comprising? and said conductive areas, said dielectric layer being a PPmember of light transparent insulative mate an integral layer ofsufliciently porous structure to rial; enable the transmission ofelectrons through said a first light transparent layer of electricallyconductive dielectric layer to said conductive layer so that saidmaterial secured to One S O said pp member; phosphor material can storea bistable electrical a second light tr ahsParent layer of electricallyeohduo charge image for an indefinite controllable time over tivematerial secured to said one side spaced from a stable range f targetvoltages applied to said Said fi st Conductive y ductive layer and saidconductive areas, and will emit a plurality of spaced light transparentareas of electri- 5 a light image corresponding to id charge i callyconductive material formed in the shape of when bombarded by electrons;Charac rs Which correspond to (iiiiereht switch p a plurality of spacedconductive lead strips each coated tions and lead portions connected tosaid characters, over the exterior f said f l portion f i secured to aOne side of said Support member in velope and electrically connected toone of the con- P insulated relationship to each other and 7 ductiveareas or to the conductive layer of said a d eOndnetiVe y storage targetinside said envelope;

a guard band of electrically conductive material secured means f rapplying different target voltages to each of to said one side of saidsupport member positioned id l d t i between said areas and said secondlayer and spaced means for generating a beam of electrons and fordetherefrom; 7 fleeting said beam across the dielectric layer of saidstorage target in response to an electrical signal to form a chargeimage of said signal on said dielectric layer; and

means for bombarding said dielectric layer substantially uniformly withelectrons to retain said charge image when said beam no longer bombardssaid dielectric layer.

11. A direct viewing bistable storage tube, for use in a cathode rayoscilloscope, comprising:

an envelope of insulating material having a transparent glass face plateportion secured to a ceramic funnel portion by a seal portion, saidfunnel portion having a plurality of spaced ridges on the outer surfacethereof extending from a point at the large end of said funnel portionadjacent said face plate to a point at the small end of said funnelportion remote from said face plate;

a storage target including a light transparent layer of conductivematerial and a plurality of spaced, light transparent areas ofconductive material, which are secured to the inner surface of said faceplate in spaced insulated relationship, and a storage dielectric layerof phosphor material supported on said inner surface of said face platewith a first portion over said conductive layer and a second portionover said conductive areas, said first portion and at least part of saidsecond portion of said dielectric layer having a thickness which iswithin the range of thickness over which said phosphor material canstore a bistable electrical charge image for an indefinite controllabletime within a stable range of target voltages on said conductive layerand said conductive areas and will emit a light image corresponding tosaid charge image, when bombarded by electrons;

a plurality of spaced metal lead strips each coated over one of theridges on the exterior of said envelope and electrically connected toone of the conductive areas or the conductive layer of said storagetarget inside said envelope;

means for applying different target voltages to each of said leadstrips, including a connector socket in the form of a collar sleeve ofinsulating material surrounding the small end of said funnel portion andhaving a plurality of metal spring contacts supported on said collar sothat they extend inwardly therefrom into contact with said lead strips;

means for generating a beam of electrons and for deflecting said beamacross the dielectric layer of said storage target in response to anelectrical signal to form a charge image of said signal on said firstportion of dielectric layer; and

means for bombarding said dielectric layer with electrons to retain saidcharge image when said beam no longer bombards said dielectric layer.

12. A direct viewing bistable storage tube for use in a cathode rayoscilloscope, comprising:

an envelope of insulating material having a transparent glass face plateportion secured to a ceramic funnel portion by a seal portion, saidfunnel portion having a plurality of spaced ridges on the outer surfacethereof extending from a point adjacent said face plate to a pointremote from said face plate;

a graticule scale provided on the inner surface of said face plate;

a storage target including a plurality of spaced light transparentlayers of conductive material and a plurality of spaced, lighttransparent areas of conductive material, which are secured to the innersurface of said face plate in spaced insulated relationship, and astorage dielectric layer of phosphor material supported on said innersurface of said face plate with a first portion over said conductivelayers and a second portion over said conductive areas so that saidfirst portion can display the signal waveforms of said oscilloscope andsaid second portion can display the switch positions of saidoscilloscope, said first portion and at least part of said secondportion of said dielectric layer having a thickness which is within therange of thicknesses over which said phosphor material can store abistable electrical charge image for an indefinite controllable timewithin a stable range of target voltages on said conductive layer andsaid conductive areas and will emit a light image corresponding to saidcharge image, when bombarded by electrons;

a plurality of annular wall coatings of conductive material coated onthe interior surface of said funnel portion of said envelope axiallyspaced along said envelope, one of said wall coatings nearest said faceplate being split into a plurality of portions which are separated byspacing gaps adjacent the spacing gaps between the conductive layers andareas of said storage target;

a plurality of spaced metal lead strips each coated over one of theridges on the exterior of said envelope and electrically connected toone of the wall coatings, wall coating portions, conductive areas or theconductive layers of said storage target inside said envelope;

means for applying different target voltages to each of said leadstrips;

means for generating a beam of electrons and for deflecting said beamacross the dielectric layer of said storage target in response to anelectrical signal to form a charge image of said signal on said firstportion of dielectric layer; and

means for bombarding said dielectric layer substantially uniform withelectrons to retain said charge image when said beam no longer bombardssaid dielectric layer.

13. An envelope structure for use in a cathode ray tube, comprising:

a hollow, tubular funnel member of ceramic material having a pluralityof spaced ridges on the outer surface of said funnel member extendinglongitudinally from a point adjacent the larger end of said funnelmember to a point adjacent the smaller end of said funnel member;

a flat face plate of light transparent glass material shaped to conformto the larger end of said funnel member;

a vacuum tight seal between said face plate and the larger end of saidfunnel member;

a plurality of lead strips of conductive material coated on said funnelmember so that they are spaced apart by said ridges; and

means for electrically connecting each of said lead strips to one of aplurality of electrodes positioned inside said envelope.

14. The envelope structure of claim 13, in combination with a connectorsocket comprising:

a collar sleeve of insulating material adapted to fit around the outsideof the smaller end of the funnel portion of said envelope;

a plurality of spring contacts of conductive material supported inspaced, insulated relationship on said collar sleeve so that they eachextend inwardly into engagement with a notch in one of the ridges onsaid funnel portion and into electrical contact with the lead strip onsaid one ridge; and

means for connecting each of said contacts to a voltage source in orderto apply different voltages to the electrodes inside said envelope.

15. A storage target comprising:

a common support member;

a plurality of storage dielectric areas supported on different portionsof said support member; and

means for simultaneously applying different D.C. voltages to thedielectric areas during the formation of charge images on said areas toenable the operation of said dielectric areas independently in storageor nonstorage conditions so that at least one of said dielectric areascan store for a controllable time a charge image produced thereon whileanother of said dielectric areas cannot store a charge image, saidvoltages being substantially uniform along each dielectric area.

16. A storage tube comprising:

an evacuated envelope;

a storage target including a plurality of storage dielectric regionssupported inside said envelope;

control means including a plurality of insulated areas of electricalconductive material adjacent different ones of said dielectric regions,and means for simultaneously applying different voltages to saidconductive areas during the formation of charge images on saiddielectric regions in order to operate said dielectric regionsindependently in storage or nonstorage conditions so that at least oneof said dielectric regions can store bistably a charge image producedthereon while another of said dielectric regions cannot store a chargeimage, said voltages being sub stantially uniform along each conductivearea;

Writing means for bombarding said storage target with high velocityelectrons to produce charge images on said dielectric regions; and

holding means for bombarding said storage target with low velocityelectrons to store the charge image on said one dielectric regionWithout necessarily storing the charge image on said other dielectricregion.

17. A direct viewing storage tube comprising:

an evacuated envelope;

a storage target including a plurality of storage dielectric regions ofphosphor material supported inside said envelope;

control means including a plurality of insulated areas of electricalconductive material adjacent different ones of said dielectric regions,and means for simultaneously applying different voltages to saidconductive areas during the formation of charge images on saiddielectric regions in order to operate said dielectric regionsindependently in storage or nonstorage conditions so that at least oneof said dielectric regions can store for a controllable time a chargeimage produced thereon While another of said dielectric regions cannotstore a charge image;

Writing means for bombarding said storage target with high velocityelectrons to produce charge images on said dielectric regions and toemit light images from said dielectric regions corresponding to saidcharge images; and

holding means for bombarding said storage target with low velocityelectrons to store the charge image on said one dielectric regionwithout necessarily storing the charge image on said other dielectricregions.

References Cited by the Examiner UNITED STATES PATENTS 2,269,156 1/42Kling 17450.52 2,623,090 12/52 Bohlke 174-5052 2,719,185 9/55 Sorg174---50.53 2,872,613 2/59 Kalfaian 3l368 2,884,558 4/59 Smith 31368DAVID G. REDINBAUGH, Primary Examiner.

DAVID J. GALVIN, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No3,214,631 October 26, 1965 Robert H Anderson r appears in the abovenumbered pat- It is hereby certified that erro s Patent should read asent requiring correction and that the said Letter corrected below.

Column 2, line 2 for "control" read correct strike out "of", firstoccurrence; column column 3, line 28, line 2 for "about" read above Yline 59, for "prevent" read prevents column 16, line '53, for "uniform"read I uniformly Signed and sealed this th day of June 1966.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner ofPatents

1. A DIRECT VIEWING STORAGE TARGET FOR USE IN A CATHODE RAY STORAGETUBE, COMPRISING: A SUPPORT MEMBER OF INSULATIVE MATERIAL; A FIRSTELECTRICALLY CONDUCTIVE AREA ON ONE PORTION OF THE SURFACE OF ONE SIDEOF SAID SUPPORT MEMBER; A SECOND ELECTRICALLY CONDUCTIVE AREA ON ANOTHERPORTION OF SAID SURFACE OF SAID SUPPORT MEMBER AND INSULAINGLY SPACEDFROM SAID FIRST AREA; AND A STORAGE DIELECTRIC LAYER OF PHOSPHORMATERIAL SUPPORTED ON SAID ONE SIDE OF SAID SUPPORT MEMBER OVER SAIDFIRST AREA AND SAID SECOND AREA, SIAD DIELECTRIC LAYER BEING AN INTEGRALLAYER OF SUFFICIENTLY POROUS STRUCTURE TO ENABLE SECONDARLY ELECTRONSEMITTED FROM ONE SIDE OF THE LAYER TO BE TRANSMITTED THROUGH SAID LAYERAND COLLECTED BY SAID CONDUCTOR AREAS ON THE OPPOSITE SIDE THEREOF SOTHAT SAID PHOSPHOR MATERIAL CAN STORE AN ELECTRICAL CHARGE IMAGE FOR ANUNLIMITED TIME OVER A STABLE RANGE OF TARGET VOLTAGES APPLIED TO SAIDFIRST AND SECOND CONDUCTIVE AREAS, AND WILL EMIT A LIGHT IMAGECORRESPONDING TO SAID CHARGE IMAGE, WHEN BOMBARDED BY ELECTRONS.